[Ric Schultz]

Here is my take:

3875 =7
modified Ncore 400 = 9
totally tweaked dual mono 4702/mosfet amp = 9.5
modified Ncore balanced = 9.5
Totally tweaked 4702/mosfet amp balanced = 9.7?

The 4702 amp has better highs than ANY Ncore but the midrange is about the same as unbalanced Ncore.  Never heard my 4702 balanced but I bet it would be as good in midrange as balanced Ncore.  Bass is probably slightly better on Ncore but on my speakers heard very little difference.

You use one stereo 4702 per channel but you don't use one half of it.  You ground the input pins to the unused channel.  Just one pair of output mosfets.  Nothing on output.....no zobel, nada...just go straight out and wrap around binding post on outside of amp.  Just us a single resistor to set bias.  Just one small compensation cap and a cap to ground in feedback.  Use separate power supply feeds (diode bridge and caps) for front end and separate power for output stage.  Use the best parts and execution (modified Wima poly caps as power supply and feedback cap bypasses are essential) and you have incredible sound.   Way better than any "chip amp".  Chip amps have extremely low bias on the output stage, have current limiting, older design, and you cannot separate the power supplies for the front end and output stage.  Run 350ma or more through a pair of mosfets and you are good to go.  Has been my reference amp for over 4 years.

[Folsom]

modified wima caps?

I think I'll be stuck with my new Amp10 for awhile. I didn't find a lot on the 4702, certainly not any PCB boards for sale.

[Folsom]

41hz Kits are not very easy to deal with. Plus they didn't even include 270r resistors I need...

[wushuliu]

41hz Kits are not very easy to deal with. Plus they didn't even include 270r resistors I need...

41hz kits are a PITA unless you are a solder professional and have measuring equipment to troubleshoot. I would go to a classdaudio (or the cheaper ebay L15 amp version), hifimediy, or TPA311X eval board from digikey before messing with 41hz.

[Folsom]

Yeah well I just fucked myself and ruined an entire 41hz audio board. Jesus...

The resistors are all labeled with brown (1%) spec'd resistors, but most of them start off with 1 as well.

Well I'm officially without music for awhile now. Useless amplifier board, useless amplifier case. At least the giant transformer I don't need on its way...

[wakibaki]

Hey, hey...

It's a rare mistake that renders a PCB completely unrecoverable. Even then you have some parts that you can re-use. I'd be surprised if you can't get a replacement PCB or other necessary parts to fix up the amp.

Amp 10 is all through hole no?

Tell us exactly what the problem is and maybe post a picture.

If you're having trouble identifying resistors, forget the markings, use a meter.

Where are you? If the worst comes to the worst you can probably get someone to fix it up for you.

w

[Folsom]

I need to get a digital meter... (I got a really old school, but nice analog).

The problem is the holes are really tiny. Without a solder rework station you can't get them clean to put in new resistors. I'd order some new resistors so I'd know the values, and they would be better, but only if I could get the holes clean. I wanted to replace the input resistors with something worth using anyhow. The design of the amplifier seems severally limited by the amount of resistors the signal must pass through.

[*Scotty*]

DoS, tooth picks are your friend here. If you can clean the holes some with solder wick and then apply some heat to hole and push the tooth pick in and let the solder cool you may be able to get your component's leads
in.
Scotty

[Folsom]

Man... They are not very big holes. I'll try tooth picks, but I certainly wouldn't be able to get one through a hole. In fact I'm worried about after-market resistors not fitting. I like to use Kiwame's in certain areas, but it probably won't be an option on this thing.

[*Scotty*]

The hole is usually only badly blocked on one side. You may have to buy a set of micro drill bits from your local hardware store and slightly enlarge the hole. Alternatively you could take some 400 grit wet and dry sandpaper and remove some of the plating on the leads to reduce their size.
Scotty

[Folsom]

I'll let you know on the tooth pick (I need to get one of those double clamps on a weight bad, I hold it all by hand). On holes that are not that small I just add solder, then use a desoldering tool. But it doesn't work on small holes because the solder doesn't flow easily enough. On larger ones all the solder goes right through and gets sucked up.

[Folsom]

Tooth picks don't work at all.

The holes are so small that the pads lift when you try to pull resistor leads out of them. I don't think even a rework station could help with this... It is a do it right the first time, or don't bother.

I guess life goes on even without a stereo. But man, I can't believe how tolerant the DIY community is of shotty crap like 41hz is up to.

[sts9fan]

Are you using wick?

[Quiet Earth]

 .  Don't feel too bad about lifting a trace. The majority of circuit boards are made to be assembled once. This goes for finished products and even cheap (inexpensive) kits.

It's too late now, but I usually use an exacto knife to open a through hole. Point the very tip of the blade into the top side of the hole and just let it rest. Then slowly, gently twirl the blade like a drill with little to no pressure. You should see some material shave away as you make a slightly bigger hole. Don't try to go all the way through, test your component first. Flip the board and repeat on the other side if needed, but use lighter pressure to avoid popping a trace. Next time you will get it. 

[Folsom]

Any sort of drilling technique sounds alright. The trouble was that some of holes were so small that I couldn't get the leads out without lifting. The lifting was happening because the leads would pull so hard on the pad. That was a problem on 4 specific ones. The rest I I got resistors out of just fine.

I'm thinking about investing in one of those SMD removal kits so I can add some of that easier flowing stuff that stays 'wet' longer. That might allow tooth picks and what not to work.